DF is currently polling the system for monitoring taskbar items, thus the CPU usage. Jon has the taskbar semi-working in the build you tried, and working a lot better in the build I have, but until he can get his hands on the actual APIs for coding a taskbar in Windows 7 (it has significantly changed from Vista and XP) this is the limited workaround that he is able to use to make it work in Windows 7 right now.
I have asked if I can quote him from a post in the Beta section, and am awaiting his reply. In the meantime, let me add *several points as to why I like DF over Ultramon (and in making this post I am not demeaning Ultramon in anyway, nor am I saying Ultramon 'sucks' - after all, I used it for 5+ years....)
1) Jon is actively working on UM, with beta numerous betas when he was making a major version revision (we had like 27 or 29, IIRC) and the changes were coming fast....
2) The cost of the software itself - it has the same functionality, and is more than 50% cheaper....
3) The ability to load random WPs from online sources as well, such a Flickr and Vladstudios....
4) The joy of Beta testing a new app that works more as *I* want it to as opposed to as how the developer only wants it to work....
5) Did I mention the price?
6) Jon's immediate reaction to any bugs that are found and / or problems that people have - he is on his forums almost nightly, if not every night, and he has even posted a method to gather information via stackTraces on the forums so that he can figure out what is going on for those with major lockup issues (which I have not had once)....